1. Field of the Invention
The present invention relates generally to read head portions of magnetic heads for hard disk drives, and more particularly to a read head having a lead overlaid magnetoresistive sensor.
2. Description of the Prior Art
One well known way to increase the performance of hard disk drives is to increase the areal data storage density of the magnetic hard disk. This can be accomplished by reducing the written data track width, such that more tracks per inch can be written on the disk. To read data from a disk with a reduced track width, it is also necessary to develop sufficiently narrow read head components, such that unwanted magnetic field interference from adjacent data tracks is substantially eliminated.
The standard prior art read head elements include a plurality of thin film layers that are deposited and fabricated to produce a GMR read head, as is known to those skilled in the art. Significantly, where the width of the thin film sensor layers that comprise the GMR read head is reduced below certain values, the magnetic properties of the layers are substantially compromised. To overcome this problem, GMR read heads have been developed in which the thin film sensor layers have an ample width and the electrical leads are overlaid on top of portions of the thin film sensor layers. This lead overlaid configuration has the effect of creating an active read head region having a width that is less than the entire width of the deposited layers, such that the magnetic properties of the thin film layers can be substantially preserved. Thus, in the lead overlaid GMR read heads of the prior art, active magnetic layer portions exist between the inner ends of the electrical leads and passive magnetic layer portions exist beneath the electrical leads.
A problem that has been recognized with regard to such prior art lead overlaid read heads is that the passive region of the magnetic layers of the read head, and particularly the free magnetic layer, is not entirely passive. That is, external magnetic fields, such as from adjacent data tracks, can create magnetic field fluctuations within the passive regions of the free magnetic layer beneath the electrical leads. When some electrical current from the overlaid leads passes through the passive sensor regions, signal noise is created. The present invention seeks to solve this problem by reducing the electrical current that passes through the passive regions of the sensor magnetic layers.
As will become clear from reading the detailed description herebelow, the present invention utilizes gold in the electrical lead overlay structure due to its superior conductivity. A problem that has occurred in the prior art where gold has been employed for magnetic head components has been that the low ductility of gold results in the creation of gold nodules and smearing at the ABS surface of the head. That is, gold structures at the ABS have a history of extruding outwardly from the ABS surface to form projecting bump-like structures termed nodules. The projecting gold will also smear across the magnetic head structures at the ABS and can electrically short the magnetic head components, leading to significant noise and ultimately the total failure of the head. The present invention solves this problem through the utilization of only thin films of gold that are applied only in small, critical areas, such that the quantity of gold is minimized and the smearing and nodule formation problems are avoided.